1. Technical Field
The present invention relates generally to electronic filters and more particularly to low noise block downconverters.
2. Discussion
Low noise block downconverters are used throughout a variety of electronic system designs to receive communication signals. Typical applications of low noise block downconverters include but are not limited to Very Small Aperture satellite Terminals (VSAT), portable satellite telephone communications terminals, point-to-point terrestrial digital radio data links, point-to-multi-point television and data broadcast transmission systems, and Direct home satellite television Broadcast Systems (DBS).
Direct home satellite television Broadcasting Systems (DBS) provide a relatively new class of television services which allows households to receive television programming directly from satellites via small satellite dishes. The size of the satellite dishes for the DBS is much smaller than its predecessors. DBS satellite dishes range from 18 inches to 3 feet in diameter, whereas predecessors typically were as large as 8 to 12 feet in diameter. The DBS satellite dishes are not moveable but instead are aimed at one position in the sky. Since the signals are digitally compressed, approximately 200 channels can currently be received by a single DBS satellite dish. The DBS satellite dish because of its smaller size can be bolted directly to the top of a home. A communications line allows the satellite dish to send processed satellite signals to a decoder box which is located inside the house.
With competition for providing DBS services to customers increasing due to their popularity, the need exists to provide a better quality signal to customers' television sets in order to continually meet customers' expectations. Also to be more commercially competitive, manufacturing costs for DBS components such as low noise block downconverters need to be minimized.
Low noise block downconverters (LNBs) are part of the 12 GHz DBS services home receiving system. Previous LNB approaches used either edge coupled or interdigitated band pass filters (BPFs). However, both of these types of band pass filters have disadvantages with respect to size, manufacturing cost, and LNB noise figure. Noise figure is the primary measurement of LNB system sensitivity to received signals, and an improved noise figure improves the quality of the signal received by the user.